The present invention relates to a device for assisted gear shifting of a transmission. More particularly, the present invention is intended to be utilized for assisted gear shifting of a transmission belonging to a boat motor.
In connection with driving arrangements for water vessels, for example in the form of motor driven leisure craft having outboard drives, an outboard drive is normally used which comprises a transmission for connecting the output shaft of the boat engine to the boat propeller shaft. The transmission may be utilized, in a known manner, to change the rotational direction of the propeller. More precisely, an adjustable gear shift control may be utilized to set the transmission in a certain operating mode which constitutes a position corresponding to forward propulsion of the boat, a position corresponding to rearward or reverse propulsion of the boat, or a neutral position.
A known transmission for outboard drives comprises a driving cogwheel which is arranged so that it is rotated by the engine""s output shaft and which transfers the power of the engine to a propeller shaft through either one of two driven cogwheels which are axially spaced apart on a vertical axle, which, in turn, is connected to the propeller shaft. For this purpose, the transmission comprises an adjustable coupling arrangement which consists of a conical clutch arranged in connection with the vertical axle. Using this clutch arrangement, one of the two driven cogwheels may be connected so that a mechanical connection is established from the engine shaft to the propeller shaft. The direction of rotation of the propeller shaft will then depend on which of the two driven cogwheels that is connected. If neither of the two driven cogwheels is connected, the neutral position is engaged.
Furthermore, the gear shift control is connected to the conical clutch by means of a mechanical push-pull wire whose inner core is influenced in a known manner either forwards or backwards when turning the gear shift control in the corresponding direction. In this manner, the transmission may be set to the desired mode of operation.
One drawback in connection with known transmissions exists in those cases when a particularly high torque is transmitted (more exactly a torque in the order of 50 Nm or higher). In such cases, a high resistance can be felt in the control during shifting of the transmission from forward to reverse or to the neutral position. This is due to the fact that the torque, which is generated by the propeller when the forward or backward position is engaged, causes a certain resistance against the axial movement of the conical clutch which is required for the transmission to be shifted from forward to rearward operation and to the neutral position.
According to a known technique, the above mentioned problem may be solved by regulating the engine in such a way that the ignition is temporarily interrupted for one or more of its cylinders when a high resistance to shifting is present. In this way, an assisted shifting is obtained in which a strongly reduced resistance is experienced.
A previously known device which provides such an assisted shifting for a transmission of a boat engine is shown in the patent U.S. Pat. No. 4,525,149. This device comprises a pivotingly suspended shifting link which may be operated by a lever for setting a reversing gear in a forward, backward or neutral position. The device further comprises a push-pull wire which is connected between a lever and a further pivotable means, which in turn is attached to the shifting link by means of a special linking means which carries a displaceable component. This displaceable component is spring biased with a certain force which corresponds to a predetermined resistance when shifting the reversing gear. Should a force exceeding this predetermined force be necessary for shifting, the displaceable component will cancel out the spring bias and be moved a small distance. This displacement may be detected using a position transducer, which will send a signal to the engine to interrupt the ignition to at least one engine cylinder. This will result in a lowered resistance during shifting.
Although the above mentioned device in principle provides a satisfactory assisted shifting, it has certain shortcomings. Foremost is the fact that it is constructed from a large number of parts, of which a plurality are pivotably arranged on the boat engine. This creates a device having an unnecessarily complicated construction and too many parts. This constitutes a negative factor regarding wear, service and cost. A further disadvantage is that a mechanical play may develop where the wire of the lever is connected to the pivotable means.
An object of the present invention is to provide an improved device for assisted shifting of a transmission, especially for a boat engine, which comprises a small number of parts, has a simple and reliable construction and has an effective functioning.
In accordance with the present invention, this and other objects have now been realized by the invention of apparatus for shifting a transmission coupled to an engine and including a controller for shifting the transmission between at least two operating modes, a control lever for switching the transmission, and an actuator for actuating the control lever in response to shifting of the controller, the apparatus comprising a first longitudinal member connected to the controller, a second longitudinal member connected to the actuator, the first longitudinal member being coaxial with the second longitudinal member, a detector for detecting relative displacement between the first and second longitudinal members, and a spring member acting between the first and second longitudinal members so as to prevent the relative displacement between the first and second longitudinal members until a force acting on one of the first and second longitudinal members exceeds the spring force of the spring member. In accordance with a preferred embodiment, the first longitudinal member is substantially tubular and the second longitudinal member comprises a substantially cylindrical slide member disposed within the first longitudinal member.
In accordance with one embodiment of the apparatus of the present invention, the spring member comprises a screw-shaped spring disposed around the second longitudinal member and within the first longitudinal member.
In accordance with another embodiment of the apparatus of the present invention, the first longitudinal member includes a first compression member and the second longitudinal member includes a second compression member, the spring member being disposed between the first and second compression members whereby the spring member is compressed between the first and second compression members when the force acting on the first and second longitudinal members exceeds the spring force of the spring member. In a preferred embodiment, the first longitudinal member is substantially tubular and the second longitudinal member comprises a substantially cylindrical slide member disposed within the first longitudinal member. In a preferred embodiment, the first longitudinal member includes a predetermined inner diameter, and the first compression member comprises a portion of the first longitudinal member having an inner diameter which is less than the predetermined inner diameter.
In accordance with another embodiment of the apparatus of the present invention, the second longitudinal member includes a predetermined inner diameter, and the second compression member comprises a portion of the second longitudinal member having an outer diameter which is greater than the predetermined outer diameter.
In accordance with another embodiment of the apparatus of the present invention, the detector comprises a position transducer, and the second longitudinal member includes at least one modified portion juxtaposed with the position transducer whereby the position transducer is adapted to detect the position of the at least one modified portion of the second longitudinal member. In accordance with another embodiment, the position transducer comprises an inductive position transducer.
In accordance with another embodiment of the apparatus of the present invention, the first longitudinal member is directly connected to the controller.
In accordance with another embodiment of the apparatus of the present invention, the second longitudinal member is connected to the control lever by means of the actuator, and the actuator includes an outer cover, the outer cover of the actuator being rigidly mounted with respect to the controller.
The present invention is intended to be used for the assisted shifting of the transmission of an engine, and comprises a first means which is connected to a lever for shifting the transmission between at least two modes of operation, a second means connected, by means of an actuator, to a control device for shifting the transmission, a detector for detecting a displacement of the first means relative to the second means, and means for limiting the power of the engine if such displacement is detected. The present invention is characterized by the fact that the first means and the second means are arranged for coaxial movement relative to each other, and the device comprises a spring means arranged to prevent such movement when a force, which is smaller than the spring force of the spring means, is acting upon the first means, and to allow said movement when the acting force is greater than that spring force.
Several advantages are achieved through the present invention. Foremost among them is the fact that the device according to the present invention has a small number of components, which results in low material, production and service costs. Furthermore, the present invention provides for completely coaxial movement of the first means relative the second means if the spring force is exceeded (i.e. movement of both means is substantially along a common axis), whilst it otherwise functions as a rigid connection between a lever and a transmission. Thus, it does not require a special arrangement for mounting in a boat, but constitutes, in principle, an extension of a wire which is attached to the above mentioned control means for the engine transmission. The device according to the present invention may further be arranged directly next to such a means, i.e. without any intermediate wire. This eliminates the risk of play at the attachment point of such a wire.